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Search: id:A037280
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| A037280 |
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If n is composite replace n by the concatenation of its nontrivial divisors [ A037279 ] then divide out any factors of 2. |
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+0
2
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| 1, 1, 3, 1, 5, 23, 7, 3, 3, 25, 11, 1173, 13, 27, 35, 31, 17, 2369, 19, 12255, 37, 211, 23, 586703, 5, 213, 39, 12357, 29, 23561015, 31, 1551, 311, 217, 57, 117345609, 37, 219, 313, 6145255, 41, 23671421, 43, 120561, 35915, 223, 47, 2933515203, 7, 251025, 317
(list; graph; listen)
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OFFSET
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1,3
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EXAMPLE
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Divisors of 12 are 1,2,3,4,6,12, so 12->2346=2*1173->1173 = a(12).
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MAPLE
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with(numtheory):ds:=proc(s) local j: RETURN(add(s[j]*10^(j-1), j=1..nops(s))):end: a:=proc(n) options remember: local d, i, l, m: if n<3 then RETURN(1) else if not isprime(n) then d:=divisors(n): l:=nops(d): m:=ds([seq(op(convert(d[l-i+1], base, 10)), i=2..l-1)]): RETURN(m/piecewise(m mod 2=1, 1, 2^(ifactors(m)[2][1][2]))) else RETURN(n) fi fi: end; seq(a(n), n=1..70); (C. Ronaldo)
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CROSSREFS
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Cf. A037279.
Sequence in context: A104053 A039512 A140825 this_sequence A133397 A096614 A011002
Adjacent sequences: A037277 A037278 A037279 this_sequence A037281 A037282 A037283
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KEYWORD
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nonn,easy,base
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Erich Friedman (erich.friedman(AT)stetson.edu).
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